Graphene-substrate Interaction On 6h-sic(0001): A Scanning Tunneling Microscopy Study

摘要

The early stage of graphene formation on the 6H-SiC(0001) surface is investigated by scanning tunneling microscopy. Islands made of a single graphitic plane form above regions of the substrate that show either a (2 × 2)_c or a (3 × 3) reconstruction. The orientations of the single-layer domains present a broad distribution of rotation angles with respect to the substrate. The atomic structures of the (3 × 3) and (2 × 2)_C substrate reconstructions are preserved under the first carbon layer. Low bias images reveal a graphitic structure, which indicates that the interaction between the first carbon plane and the SiC surface is comparatively much weaker on the C face than on the Si face of the substrate. The coupling is stronger on the (2 × 2)_C surface reconstruction than on the (3 × 3) one, where an almost ideal graphene structure is found close to the Fermi level.